1. Field of the Invention
The present invention relates to an electrolytic solution including a solvent and an electrolyte salt and a battery using the electrolytic solution.
2. Description of the Related Art
In recent years, portable electronic devices such as camera-integrated VTRs (videotape recorders), cellular phones, or laptop computers are widely used, and size and weight reduction in the portable electronic devices and an increase in longevity of the portable electronic devices have been strongly demanded. Accordingly, as power sources for the portable electronic devices, the development of batteries, specifically lightweight secondary batteries capable of obtaining a high energy density have been promoted. Among them, a secondary battery (a so-called lithium-ion secondary battery) using insertion and extraction of lithium for charge-discharge reaction, a secondary battery (so-called lithium metal secondary battery) using precipitation and dissolution of lithium, or the like holds great promise, because the secondary batteries are capable of obtaining a large energy density, compared to a lead-acid battery or a nickel-cadmium battery.
As an electrolytic solution for the lithium-ion secondary battery and the lithium metal secondary battery, a combination of a carbonate-based solvent such as propylene carbonate or diethyl carbonate and an electrolyte salt such as lithium hexafluorophosphate is widely used. It is because the combination has high conductivity, and its potential is stable.
In addition, to improve various performance capabilities, some techniques relating to the compositions of electrolytic solutions used in these secondary batteries have already been proposed. More specifically, to improve cycle characteristics or safety, a technique of including a chain carbonate including a halogen is known (for example, refer to Japanese Patent No. 3294400). Moreover, to improve high-temperature storage characteristics, initial charge-discharge characteristics, safety characteristics, cycle characteristics or the like, techniques of including a chain carbonate dimer, a chain carboxylate dimer, a chain sulfonate dimer, or a phosphate are known (for example, refer to Japanese Patent No. 3393620, and Japanese Unexamined Patent Application Publication Nos. 2000-182669, 2001-085056, 2004-079426, 2007-005242, 2006-351337, 2006-004746 and 2006-004747). Further, to improve cycle characteristics, a technique of including a cyclic carbonate including a halogen and a chain carboxylate dimer is known (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-172811).